1. Field of the Invention
The present invention relates to the fabrication of nanometer-size wires useful as interconnects between levels in microelectronic devices, as non-linear optical devices, and as arrays of sharp field emitters for vacuum microelectronics, including field emission video displays.
2. Description of Related Art
Creation of nanometer-size wires with large length-to-diameter ratios has previously been accomplished using various lithographic techniques to form a cylindrical or square hole in a resist material and using this hole as a mold for forming a wire. Presently, focused electron beams, focused ion beams, and UV photons can be used to create wires with dimensions down to 100-200 nm. Nuclear or ion track lithography, which relies on the etching of the cylindrical latent tracks created in a material, has been used to create nanometer-sized wires, i.e., wires with diameters smaller than 100 nm. Of the wires produced using nuclear track lithography, the smallest diameter reported is approximately 8 nm [Williams and Giordano, Fabrication of 80 Angstrom Metal Wires, Rev. Sci. Instrum. 55 (3), 410 (1984)]. Furthermore, the relatively small nanometer-sized wires are produced if the nuclear tracks are annealed prior to etching. Nevertheless, all such methods involve etching the latent tracks to remove a volume of material along the ion trajectory prior to filling the etched track space with the wire material by coating and/or electroplating.
The present invention involves the production of nanofilaments or nanometer-size (cross-sectional) wires having diameters of less than about 5 nm, and preferably above 0 to 2 nm, that are particularly useful as interconnects between levels in microelectronic devices, as non-linear optical devices, and as field emitters for vacuum microelectronics and video displays.
The present invention includes such small novel wires and a method for producing such wires. Steps in the method include forming a latent nuclear or ion track in a trackable material, infiltrating the latent track with an atomic species that has essentially no mutual solubility with the trackable material, and annealing the tracked material containing the infiltrated latent track at relatively high temperatures to form a wire within the volume of the latent track. Also, prior to infiltration, the eventual diameter of the wire can be controlled by partial, pre-annealing the latent track volume at temperatures between those of infiltration and final annealing. An advantage of the invention allows the preparation of such wires without etching latent tracks in the trackable material. The method relies on the thermally driven self-assembly of atomic species after infiltration into the latent nuclear tracks. The wires comprise the infiltrated atomic species and usually have diameters of above about 0.1 to about 8 nm with high aspect ratios; however, in a highly preferred embodiment, the resultant nanowires have diameters less than 8 nm, and preferably less than 1 nm, such as about 0.3 to about 0.5 nm. Such small wires can provide essentially one-dimensional quantum confinement or less, including monocrystalline nanowires and quantum dots.